Dimethyl ether blended fuel alternative for diesel engines

ABSTRACT

A dimethyl ether blended fuel having a fuel composition including dimethyl ether (DME), glycerol, and a co-solvent, wherein the fuel composition achieving a kinematic viscosity of at least 0.2 centistokes (cSt).

CROSS-REFERENCE TO RELATED APPLICATIONS

This PCT application claims the benefit of Provisional Application No. 62/323,953, filed Apr. 18, 2016. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to improvement of the viscosity of dimethyl ether through blending with glycerol and oxygenated co-solvents.

BACKGROUND AND SUMMARY

This section provides background information related to the present disclosure which is not necessarily prior art. This section also provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

Diesel fuel is a liquid fuel used in diesel engines, noted for its ability to combust through compression alone without a spark, and widely used for vehicles and stationary installations worldwide. It is most commonly made from petroleum and is energetically more favorable than gasoline. However, its combustion in compression ignition engines tends to produce much more soot than does the combustion of gasoline in spark ignition engine. Due to the high amount of soot emission, diesel fuel is currently burned in compression ignition engines with the use of diesel particulate filter (DPF) and electronic unit to control the operation of DPF, which adds to both the complexity and cost of the after-treatment system.

Dimethyl ether (DME) is a chemical that could potentially serve as an alternate to petroleum diesel, with advantages of a high cetane number (indicating faster combustion speed) as well as very low emissions meeting environmental regulations. However, DME by itself does not have the viscosity of standard diesel, and thus any engine fuel system using DME must be specially designed or highly customized.

Dimethyl ether (DME) is a potential petroleum diesel fuel replacement that can eliminate soot and other particulate emissions and has a high cetane number indicating improved ignitibility. However, DME has extremely low viscosity compared to standard diesel, and its use in vehicles requires special modifications to fuel injection and management systems. A new DME fuel blend now seeks to overcome that obstacle, bringing viscosity to ASTM standards for No. 1 and No. 2 diesel (depending on the mixture composition) while preserving the clean combustion benefits for use in existing diesel engines with minimal modification.

The present invention is two types of homogeneous mixtures of DME and glycerol with addition of two different co-solvents to make DME and glycerol miscible and viscous enough to meet ASTM (an international standards organization) requirements for No. 1 or No. 2 diesel oil (ASTM D975), the standard diesel used for transportation purposes. Di-propylene glycol (DPG) and propylene glycol (PG) are used as co-solvents and this resulted in two different homogeneous ternary solutions: DME, DPG and glycerol and DME, PG and glycerol. This would allow current diesel engines to use the blended DME fuel with little to no modifications. This could make DME a more attractive alternative to petroleum diesel, especially as the European Union looks to find a standard alternative biofuel by 2030.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

The principles of the present teachings provide a dimethyl ether blended fuel employing di-propylene glycol (DPG) or propylene glycol (PG) to improve the miscibility of DME (very low viscosity) with glycerol (highly viscous). This results in two types of homogeneous blends that both meet ASTM D975 kinematic viscosity specifications while remaining largely DME (near 50%). Table 1 shows the kinematic viscosity standard for No. 1 diesel and No. 2 diesel in ASTM D975.

TABLE 1 No. 1 Diesel No. 2 Diesel (For all sulfur grades) (For all sulfur grades) Min. Kinematic Viscosity 1.3 1.9 (@40° C.), [cSt] Max. Kinematic Viscosity 2.4 4.1 (@40° C.), [cSt]

For DME/DPG/glycerol mixture, experimental measurement shows that

$54\mspace{14mu} {{wt}.\mspace{14mu} \%}\mspace{14mu} \left( {\frac{{{mass}\mspace{14mu} {of}\mspace{14mu} {DPG}} + {{mass}\mspace{14mu} {of}\mspace{14mu} {glycerol}}}{{{mass}\mspace{14mu} {of}\mspace{14mu} {DPG}} + {{mass}\mspace{14mu} {of}\mspace{14mu} {glycerol}} + {{mass}{\mspace{11mu} \;}{of}\mspace{14mu} {DME}}} \times 100} \right)$

addition of binary mixture of DPG and glycerol (34.02 wt. % DPG+19.98 wt. % glycerol) into DME meets the minimum kinematic viscosity level for No. 1 diesel oil (1.3 cSt) while 60 wt. % addition of binary mixture of DPG and glycerol (35.40 wt. % DPG+24.6 wt. % glycerol) meets the minimum kinematic viscosity level for No. 2 diesel oil (1.9 cSt). For DME/PG/glycerol mixture, experimental measurement shows that 52 wt. % addition of the binary mixture of PG and glycerol (34.05 wt. % PG +17.94 wt. % glycerol) meets the minimum kinematic viscosity level for No. 1 diesel oil while 58 wt. % addition of the binary mixture of PG and glycerol (36.11 wt. % PG+21.88 wt. % glycerol) meets the minimum kinematic viscosity level for No. 2 diesel oil. The use of fuel additives such as Lubrizol 539 can overcome other issues such as lubricity. This DME blend fuel will bring improved engine durability over engines operating on neat DME and improved performance with cleaner combustion over conventional diesel fuels.

It should be understood that the present teachings are not limited to the aforementioned mixtures with specific mixture composition. In some embodiments, the present teachings may provide a range of acceptable performance capable of meeting ASTM D975 standards. These teachings provide two different ternary blends (1.DME/Glycerol/PG and 2.DME/Glycerol/DPG) at various possible mixture composition preventing the phase separation. Table 2 shows the minimum co-solvent (DPG or PG) weight % in two different ternary blends to ensure the homogeneous phase of the ternary solution, and this defines the range of our invented ternary blends.

TABLE 2 Weight % Minimum co-solvent Resulting of DME in wt. % in ternary viscosity Type of Co- the ternary blend to ensure of the ternary solvent blend homogeneous phase solution [cSt] Di-propylene 91.9%  6.4% 0.215 Glycol (DPG) 82.2% 14.1% 0.279 69.6% 22.7% 0.360 60.1% 28.5% 0.613 57.6% 29.1% 0.665 50.0% 33.1% 1.050 40.9% 35.0% 1.840 Propylene 90.0%  7.6% 0.222 glycerol (PG) 70.0% 21.8% 0.434 58.0% 28.7% 0.745 50.0% 32.8% 1.103 39.2% 37.9% 2.427

The present invention accommodates both aerosol grade and fuel grade DME. Fuel grade DME will contain H2O. The present invention yields stable, homogeneous ternary solutions in the presence of as much as 5 wt. % H2O in the DME used to make the DME blend fuel.

The present invention increases the viscosity of dimethyl ether, DME, (a promising, near commercial, ultra clean, replacement diesel fuel) to enable use of DME in conventional diesel fuel injection systems with a modest amount of conversion of the fuel system.

Today, dedicated diesel fuel injection systems, designed specifically for DME, are needed to employ DME in diesel engines. Volvo Trucks, Hino Motors, Nissan Truck, Isuzu and others have been pursuing the development of neat DME engines for more than a decade. In all of these engine and vehicle systems, the fuel injection hardware must be designed from the ground up or be heavily modified to accommodate DME. The reason for this is the lack of lubricity and the very low viscosity (0.2 cSt at 40° C., versus 2.5 cSt typically for diesel fuels). Lubricity can be increased using commonly available fuel additives (e.g., Lubrizol 539), but viscosity has only been able to be increased through aggressive blending with other fuels and chemicals.

Blends as high as 75% by mass in another lubricious compound or mixture (e.g., diesel fuel) are needed to meet the minimum kinematic viscosity required in the ASTM D975 specification for No. 2 diesel fuels. Glycerol has a very high viscosity but has limited miscibility in DME. A mixture of glycerol (˜180 cSt at 40° C.) and DME can achieve a commensurate viscosity compared to No. 1 or No. 2 diesel oil by using glycol co-solvents. Two types of the glycol co-solvents are found: di-propylene glycol (DPG) and propylene glycol (PG). For DME/DPG/glycerol mixture, experimental measurement shows that 54 wt. mass of DPG+mass of glycerol/mass of DPG+mass of glycerol+mass of DME×100) addition of binary mixture of DPG and glycerol (34.02 wt. % DPG+19.98 wt. % glycerol) into DME meets the minimum kinematic viscosity level for No. 1 diesel oil (1.3 cSt) while 60 wt. % addition of binary mixture of DPG and glycerol (35.40 wt. % DPG+24.6 wt. % glycerol) meets the minimum kinematic viscosity level for No. 2 diesel oil (1.9 cSt). For DME/PG/glycerol mixture, experimental measurement shows that 52 wt. % addition of the binary mixture of PG and glycerol (34.05 wt. % PG+17.94 wt. % glycerol) meets the minimum kinematic viscosity level for No. 1 diesel oil while 58 wt. % addition of the binary mixture of PG and glycerol (36.11 wt. % PG+21.88 wt. % glycerol) meets the minimum kinematic viscosity level for No. 2 diesel oil. Further testing to discover a more effective co-solvent might demonstrate higher viscosity that exceeds the minimum ASTM kinematic viscosity of No. 2 diesel oil with lower concentration of binary mixture of co-solvent and glycerol.

The present invention employs alcohol or ether co-solvent that allows glycerol to be dissolved into DME, permitting the high viscosity of glycerol to benefit mixtures with DME and achieve the minimum ASTM D975 kinematic viscosity specification.

Currently, diesel engines must be converted to DME operation by using dedicated fuel injection systems designed for use with DME. The present invention could allow current diesel fuel injection systems to operate on DME, with only the elastomeric components being changed over to DME compatible materials.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A dimethyl ether blended fuel comprising: a fuel composition having dimethyl ether (DME), glycerol, and a co-solvent, wherein the fuel composition having a kinematic viscosity of at least 0.2 centistokes (cSt).
 2. The dimethyl ether blended fuel according to claim 1 wherein the fuel composition having a kinematic viscosity of at least 1.3 centistokes (cSt)
 3. The dimethyl ether blended fuel according to claim 1 wherein the fuel composition having a kinematic viscosity of at least 1.9 centistokes (cSt)
 4. The dimethyl ether blended fuel according to claim 1 wherein the co-solvent comprises Di-propylene glycol (DPG).
 5. The dimethyl ether blended fuel according to claim 4 wherein the fuel composition having a binary mixture of DPG and glycerol of about 54 wt. %.
 6. The dimethyl ether blended fuel according to claim 5 wherein the binary mixture of DPG and glycerol has about 34.02 wt. % DPG and 19.98 wt. % of glycerol.
 7. The dimethyl ether blended fuel according to claim 4 wherein the fuel composition having a binary mixture of DPG and glycerol of about 60 wt. %.
 8. The dimethyl ether blended fuel according to claim 7 wherein the binary mixture of DPG and glycerol has about 35.40 wt. % DPG and 24.6 wt. % of glycerol.
 9. The dimethyl ether blended fuel according to claim 1 wherein the co-solvent comprises propylene glycol (PG).
 10. The dimethyl ether blended fuel according to claim 9 wherein the fuel composition having a binary mixture of PG and glycerol of about 52 wt. %.
 11. The dimethyl ether blended fuel according to claim 10 wherein the binary mixture of DPG and glycerol has about 34.05 wt. % PG and 17.94 wt. % of glycerol.
 12. The dimethyl ether blended fuel according to claim 9 wherein the fuel composition having a binary mixture of PG and glycerol of about 58 wt. %.
 13. The dimethyl ether blended fuel according to claim 12 wherein the binary mixture of DPG and glycerol has about 36.11 wt. % PG and 21.88 wt. % of glycerol.
 14. The dimethyl ether blended fuel according to claim 1 wherein the DME comprises water.
 15. The dimethyl ether blended fuel according to claim 14 wherein the DME comprise 5 wt. % water.
 16. The dimethyl ether blended fuel according to claim 1, wherein the fuel composition comprises 6.4 to 35 wt. % DPG and 39.2 to 91.9 wt. % DME, and the kinematic viscosity is between 0.2 to 1.84.
 17. The dimethyl ether blended fuel according to claim 1, wherein the fuel composition comprises 7.6 to 37.9 wt. % PG and 39.2 to 91.9 wt. % DME, and the kinematic viscosity is between 0.2 to 2.43 cSt. 